Alright, here's a working example. It's not very clean, but it functions properly.
http://www.fortress-forever.com/publ...v_security.zip
It uses a trigger_ff_clip to block players, a non-solid func_brush for the visuals, and a trigger_hurt 1 unit inside the trigger_ff_clip to kill any offense that is inside the security when it goes up (so they don't get stuck inside). This also means that offense doesn't get killed if they touch the lasers from the outside when security is up; if you don't like that, just extend the trigger_hurt to overlap with the trigger_ff_clip.
The Lua code is somewhat complex, but you should be able to use it without modifying much (put any custom OutputEvent()'s or anything like that in the ClipSec_Event_SecurityOn/ClipSec_Event_SecurityOff functions at the bottom).
The func_button approach I used I'm not very fond of (I've never made a security map, but I think it's ill-advised to have the func_button reset delay dictate how long security goes down for as that should be controlled by Lua ideally). That is something that can really be improved.
I'll look into adding a Disable and Enable input for trigger_ff_clips, as that would make this whole thing immensely cleaner, easier, and more intuitive.